The present invention relates in general to devices such as receivers and sensors for spatial positioning systems and in particular to devices for spatial positioning systems having tunable measurement filters.
Spatial positioning systems provide a convenient tool for taking accurate measurements such as distance, angle, or position. Basically, one or more transmitters emit signals that are detected by a receiver deployed about a work site. The receiver processes the emitted signals and determines a measurement therefrom. Alternatively, some devices for spatial positioning systems, such as certain tilt sensors, derive measurements without the need for a separate transmitter. In either respect, the determined measurement signals are typically output to a display or provided as a feedback signal to a control system. The flexibility and accuracy of spatial positioning systems has made such systems suitable for use in a number of diverse applications including for example, building and general construction, earthmoving, surveying, navigating, vessel and structure placement and other applications where it is desirable to accurately take measurements.
Presently, receivers for spatial positioning systems provide signal conditioning and filtering to improve the reliability of measurements taken thereby. However, the receiver filter operates on a ‘one-size’ fits all approach regardless of application or environment. While fixed filter receivers may be satisfactory for removing noise under some conditions, there are situations where a fixed filter receiver may not provide optimal results. For example, operating environments may have drastically different and dynamically changing noise levels due to beam bounce, electrical interference, weather conditions, such as gusts of wind, and operational conditions, such as vibration and operator handling. A receiver having a filter tuned properly to filter out noise due to a relatively high frequency vibration may be ineffective at filtering relatively low frequency noise resulting from beam bounce. However, a filter that is suitable for filtering relatively low frequency noise, such as produced by beam bounce, may have excessive lag that makes the processing delay due to the filter performance impractical, such as for real-time control operations.